Title
Resolution to Approve the Purchase of Two Allen Bradley, Power Flex 700, Variable Frequency Drives from McNaughton-McKay Electric Co. for Effluent Pump Motors at the Wastewater Treatment Plant ($45,000.00)
Memorandum
Your approval is requested to authorize a purchase order with McNaughton-McKay Electric Company for the acquisition of two variable frequency drives (VFDs) to replace two failing, obsolete VFDs on effluent pump motors at the Wastewater Treatment Plant (WWTP) in the amount of $45,000.00.
VFDs are used to improve energy efficiency and maximize operational control of alternating current motors. The WWTP uses Allen Bradley, 1336 Classic, VFDs to control 150 H.P., effluent pump motors in the plant’s water reclamation process tertiary treatment. Failure of a VFD at this stage in the process would be detrimental to control of effluent flow to the sand filters and ultra-violet disinfection system. Plant energy utilization would also be adversely impacted by such a failure.
These particular machines were installed 30 years ago and have exceeded their useful life. Over the past five years the VFDs have failed several times for reasons associated with the electronic circuit boards and power transistors. The Allen Bradley,1336 Classic, VFD is listed by the manufacturer as a discontinued and obsolete product. Since the manufacture of Allen Bradley, 1336 Classic, VFDs has been discontinued, the production of circuit boards for the drive has ceased. No new circuit boards are available. A faulty circuit board has to be returned to the manufacturer for repair at a cost that represents a large fraction of the cost of a new VFD.
WWTP staff has worked with engineers from McNaughton-McKay Electric Co. and Rockwell Automation, the parent company of Allen Bradley, to determine if retrofitting a new VFD into the existing drive enclosure with its associated manual and by-pass control circuits was feasible. After investigation, it was determined that an Allen ...
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